The present invention relates in general to the field of intaglio printing and engraving, and more particularly, to a continuous intaglio printing apparatus and multi-station system enabling the use of a continuous web of material, e.g., letterhead paper or business card stock, to which various indicia of single or multiple colors is engraved on registered portions of the web prior to severing or die cutting into individual sheets of letterhead paper or business cards of regular or irregular shape.
As used herein, the terms intaglio and engraving are intended to have the same meaning and are therefore used interchangeably. The conventional practice in the intaglio printing and engraving art is to engrave print paper or card stock in individual precut pieces. The process of intaglio printing or engraving is generally performed in a single die stamping operation, such as known from Gabbert, U.S. Pat. No. 2,623,457. However, it is also known that multiple engravings can be achieved in a single die stamping operation. In this regard, multiple engraving operations almost always require secondary cutting operations which result in increased costs and the creation of additional process operations where errors can occur, resulting in a higher percentage of product rejection. When there is a requirement for engraving more than one color, or providing some form of embossing and foil, additional passes through the engraving press are necessary, again resulting in additional processing operations that increase costs and rejects. It is not surprising that the standard engraving art makes color registration during additional passes very difficult and heavily dependent upon the skill of the operator.
One advance in the intaglio printing and engraving art is the design of engraving presses which accommodate the use of a continuous web of paper or card stock which is subsequently severed into single engraved sheets or cards. Conventional engraving presses of this type are known from Rosenthal, U.S. Pat. No. 1,960,513 and Rosenthal, U.S. Pat. No. 2,037,091. Once again, these engraving presses require added process operations that increase costs and rejects when required to perform additional passes through the engraving press, for example, in multi-colored engraving. In addition, the same scenario occurs when additional passes are required for separately engraving various portions of the paper or card stock which cannot be achieved using a single engraving die. One can appreciate that the known intaglio printing and engraving art has yet to address the problems associated with multiple engraving operations and the requirement for precise registration of the paper or card stock with the engraving die.
The known engraving presses are constructed to provide the intermittent movement of the engraving die by the press ram using mechanical action. Mechanical presses although having been used in the engraving art for many years, possess a number of inherent disadvantages. In particular, mechanical presses are frequently slow due to their long operating stroke which often cannot be adjusted. Dwell time, i.e., the time the engraving die is maintained in pressure contact with the paper or card stock, is not an operating variable of a mechanical press. That is, the mechanical linkage results in an instantaneous contact force being applied by the engraving die into the paper or card stock as the linkage goes through its operating stroke. However, due to the properties of certain printing inks and absorption characteristics of certain paper or card stocks, it may be desirable to have a dwell time to enhance the transfer of the printing ink from the engraving die onto the paper or card stock.
As mechanical presses bottom out after the top of their operating stroke, unless the linkage is properly adjusted, there is a tendency for these presses to lock up thereby interrupting the engraving process. This tendency is increased when it is desired to adjust the ram force by changing the spaced distance between the ram and the stationery platen. If the resulting space is not sufficient to enable the linkage to go through its full cycle, the press will lock up. Thus, there have been substantial unmet needs in the intaglio printing and engraving art in providing a continuous multi-station intaglio printing system, apparatus and method therefor which address and overcomes the above problems with a high degree of repeatability and control which has heretofore been unknown.